Hydridosilapyrroles, hydridosilaazapyrroles, thiasilacyclopentanes, method for preparation thereof, and reaction products therefrom

ABSTRACT

Hydridosilapyrroles and hydridosilaazapyrrole are a new class of heterocyclic compounds having a silicon bound to carbon and nitrogen atoms within the ring system and one or two hydrogen atoms on the silicon atom. The compounds have formula (I): 
                         
in which R is a substituted or unsubstituted organic group and R′ is an alkyl group. These compounds react with a variety of organic and inorganic hydroxyl groups by a ring-opening reaction and may be used to produce silicon nitride or silicon carbonitride films.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of co-pending U.S. patent applicationSer. No. 15/176,703, filed Jun. 8, 2016, which claims priority to U.S.Provisional Application No. 62/180,351, filed Jun. 16, 2015, thedisclosures of which are herein incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION

There is currently a great deal of interest in molecular layerdeposition for nano-featured devices, including semiconductors andmicroelectromechanical systems (MEMS). Rapid and preferably quantitativedeposition of single molecular layers with a minimum of byproducts isdesirable. Silicon carbonitride films are of particular interest for avariety of dielectric, passivation and etch-stop applications.

Examples of known systems to produce silicon nitride or siliconcarbonitride films include that described in U.S. Pat. No. 4,200,666using trisilylamine ((SiH₃)₃N) and an inert gas with optional ammonia;the system of diethylsilane and ammonia in an LPCVD system at 800° C. asdescribed in A. Hochberg et al. (Mat. Res. Soc. Symp, 24, 509 (1991));and the system of cyclic silazanes and ammonia in a chemical vapordeposition (CVD) process described by B. Arkles (J. ElectrochemicalSoc., Vol. 133, No. 1, pp. 233-234 (1986)).

More recently, halide-containing precursors such as tetraiodosilane andhexachlorodisilane have been described in U.S. Pat. No. 6,586,056 and byM. Tanaka et al. (J. Electrochemical Society, 147, 2284 (2000)),respectively. Unfortunately, there are operational difficultiesassociated with the corrosiveness of the precursors, as well as withfilm contaminants and byproducts.

Another approach is the use of bis(t-butylamino)silane, which producesSiN films of reasonable quality at temperatures as low as 550° C. (J.Gumpher et al., J. Electrochem. Soc., 151, G353 (2004)) or in aplasma-assisted pulsed deposition method as described in U.S. PatentApplication Publication No. 2011/0256734. In both cases, there arecomplications with carbon contamination of films and the high energyrequirements of both the thermal and plasma regimes, which are notcompatible with substrate stability. A review of other alternativeapproaches is found in EP 2 644 609 A2, which suggests fluorinatedprecursors. While such fluorinated precursors theoretically allow lowerdeposition temperatures, the introduced fluorine frequently affectselectrical properties of silicon based structures.

Known cyclic azasilanes contain alkyl (e.g., methyl) or alkoxy (e.g.,ethoxy) substitution on the silicon atom (see B. Arkles et al., “CyclicAzasilanes: Volatile Coupling Agents for Nanotechnology” in Silanes andOther Coupling Agents, Vol. 3, K. Mittal (Ed.) VSP (Brill), pp. 179-191(2004)). In the primary applications of interest, these compounds areunacceptable because they either contain excessive levels of carbon orintroduce oxygen into the film due to substitution at the silicon atomon the ring. Thus, the need for new silicon nitride and siliconcarbonitride precursors that deposit silicon nitrides at low temperaturehas still not been satisfied.

BRIEF SUMMARY OF THE INVENTION

A hydridosilapyrrole or hydridosilaazapyrrole according to an embodimentof the invention has formula (I):

wherein R is a substituted or unsubstituted organic group having acarbon or silicon atom bonded to the pyrrole ring nitrogen and R′ is analkyl group.

A method of producing a hydridosilapyrrole or hydridosilaazapyrrolehaving formula (I):

wherein R is a substituted or unsubstituted organic group having acarbon or silicon atom bonded to the pyrrole ring nitrogen and R′ is analkyl group, the method comprising reducing a cyclic azasilane having analkoxide group on the silicon.

A thiasilacyclopentane having formula (II):

wherein R″ and R′″ are independently hydrogen or an alkyl group.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to a new class of cyclic azasilanes known ashydridosilapyrroles (or cyclic azasilylhydrides) and hydridoazapyrroles.Unlike known cyclic azasilanes which contain alkyl or alkoxysubstituents on the silicon atom, the inventive materials are a class ofhydridosilanes which can reduce or eliminate the carbon and oxygencontributions from substitution on the silicon atom.

The hydridosilapyrroles and hydridoazapyrroles according to theinvention have a general structure shown in formula (I):

Essential features of these compounds include a five atom ring structurein which a silicon atom within the ring is bonded to both a carbon and anitrogen atom and at least one hydrogen atom is bonded to the siliconatom. As shown in Formula (I), the nitrogen may be bonded to a carbon orto a second nitrogen in the ring, forming a cyclic diazasilane (alsocalled a hydridosilaazapyrrole or diazasilacyclopentane).

In formula (I), R may be any substituted or unsubstituted organic groupin which a carbon or silicon is bonded to the ring nitrogen. Exemplarygroups include, without limitation, alkyl groups, aryl groups, esters,chiral organic groups and trimethylsilyl groups. Preferred are smallhydrocarbon radicals having up to six carbon atoms (including phenyl)and nitrogen-substituted hydrocarbons such as dimethylaminoethyl. R′ maybe any alkyl group preferably having up to about twenty carbon atoms,more preferably less than about six carbon atoms, most preferablymethyl, ethyl, propyl, or butyl.

Simple specific examples of inventive compounds includeN-methyl-2-silapyrrole and N-butyl-2-silapyrrole:

Other examples include those having more complex functionalsubstitutions at the nitrogen, including chiral phenethylamines,trimethylsilyl groups and tertiary amine groups.

In one embodiment, the ring structure also contains an additionalnitrogen atom in the 3 position, forming cyclic diazasilanes. Twoexemplary cyclic diazasilanes include:

The invention also relates to a method for producing thehydridosilapyrroles described above. The method involves reducing thecorresponding cyclic azasilanes having alkoxide substitution on thesilicon atom, as shown in the following exemplary scheme:

Thus, the only limitation on the hydridosilapyrroles which may beproduced according to the method of the invention is the ability tosynthesize the alkoxy-containing precursor.

The inventive materials react quantitatively via a ring-opening reactionwith both inorganic and organic hydroxyl groups, including hydroxylgroups on siliceous, aluminum, and titanium substrates, as shown below,and with organic hydroxyl groups, including alcohols.

These materials may also react with isolated silanols, such astriethylsilanol, in homogeneous solutions, and are also capable ofreacting with other protic species, including amines and mercaptans.

The silyl hydride functionality may remain intact or, depending on thedesired end-product, may be dehydrogenated to form siliconcarbonitrides, may be utilized as a regiospecific reducing agent, or mayundergo hydrosilylation. Thus, the inventive materials are attractivefor many applications, including the formation of silicon nitride andsilicon carbonitride films.

The invention also relates to a new class of thiasilacyclopentanecompounds having formula (II):

In Formula (II), R″ and R′″ are independently hydrogen or an alkyl groupcontaining about one to about twenty carbon atoms, most preferablyhydrogen or methyl. A preferred compound of this class is1-thia-2-silacyclopentane shown below; other preferred and exemplarycompounds of this class are also shown below. In these structures, R″and R′″ are preferably hydrogen or methyl:

Thiasilacyclopentanes undergo reactions with hydroxylic surfacesgenerating films containing mercaptan groups. The mercapto groups formedin this reaction can reacted with olefins or other mercapto-compounds tofurther modify the surfaces.

The thiasilacyclopentane compounds according to the invention aredescribed by a method which is analogous to that described above forproducing hydridosilapyrroles: by the reduction of thiasilacyclopentanecompounds having alkoxide group(s) on the silicon. For example,1-thia-2-silacyclopentane is prepared from2,2-alkoxy-1-thia-2-silacyclopentane, shown below, as a startingmaterial:

The invention will now be described in connection with the followingnon-limiting examples.

Example 1: Synthesis of N-butyl-2-silapyrrole(n-Butyl-azasilacyclopentane)

Under an argon atmosphere, a 2-liter 4-necked flask equipped with acooling bath, mechanical stirrer, pot thermometer, addition funnel, anddry-ice distill head was charged with 400 ml of 2-methyltetrahydrofuran,followed by 25.3 g (0.67 mol) of lithium aluminum hydride portion wise.The mixture was cooled to −10° C. and 203.4 g (1.0 mol)N-n-butyl-aza-dimethoxysilacyclopentane were added via addition funnelbetween −5 to 0° C. over 2 hours. After completion of the addition, thepot mixture was maintained at 0° C. for about 2 hours. 345 g of mineraloil was added into the pot. The pot mixture was stripped at a pottemperature of 80° C. at 0.5 mmHg. Redistillation of the crude productunder reduced pressure provided 68.1 g (48% yield) of the titlecompound, b.p.: 60 2/25 mmHg, density@20° C.:0.783, FTIR: vS-H:2120.0(vs).

Example 2: Synthesis of N-(3-Dimethylaminopropyl)-2-methyl-2-silapyrrole(N-Dimethylaminopropyl-Aza-1-Methyl-silacyclopentane)

Under an argon atmosphere, a 2-liter 4-necked flask equipped with acooling bath, mechanical stirrer, pot thermometer, addition funnel, anddry-ice distill head was charged with 300 ml of 2-methyltetrahydrofuran,followed by 9.5 g (0.25 mol) of lithium aluminum hydride portion wise.The mixture was cooled to −10° C. and 162.3 g (0.75 mol)N-n-dimethylaminopropyl-aza-methylmethoxysilacyclopentane was added viaaddition funnel between −5 and 0° C. over 2 hours. Upon completion ofthe addition, the pot mixture was kept at 0° C. for about 2 hours. 260 gof mineral oil was added into the pot. The pot mixture was stripped at apot temperature of 80° at 0.5 mmHg. Redistillation of product crudeunder reduced pressure provided the title compound, b.p.: 52-4/0.5 mmHg,density@20° C.: 0.857, FTIR: vS-H:2111 (vs).

Example 3: Synthesis of N-Trimethylsilyl-2-silapyrrole(N-Trimethylsilyl-Aza-1-Methyl-Silacyclopentane)

Under an argon atmosphere, a 2-liter 4-necked flask equipped with acooling bath, mechanical stirrer, pot thermometer, addition funnel, anddry-ice distill head was charged with 400 ml of 2-methyltetrahydrofuran,followed by 25.3 g (0.67 mol) of lithium aluminum hydride portion wise.The mixture was cooled to −10° C. and 203.4 g (1.0 mol)N-trimethylsilyl-aza-dimethoxysilacyclopentane was added via additionfunnel between −5 to 0° C. over 2 hours. Upon completion of theaddition, the pot mixture was kept at 0° C. for about 2 hours. 345 g ofmineral oil was added into the pot. The pot mixture was stripped at apot temperature of 80° at 0.5 mmHg. Redistillation of product crudeunder reduced pressure provided the title compound, b.p.: 48-50/10 mmHg,density@20° C.: 0.846, FTIR: vS-H:2120 (vs).

Example 4: Synthesis of 1-Thia-2-silacyclopentane

Under an argon atmosphere, a 2-liter 4-necked flask equipped with acooling bath, mechanical stirrer, pot thermometer, addition funnel, anddry-ice distill head was charged with 490 ml of diglyme, followed by27.8 g (0.0.73 mol) of lithium aluminum hydride portion wise. Themixture was cooled to −10° C. and 200.4 g (1.22 mol) of2,2-dimethoxy-1-thia-2-silacyclopentane was added via addition funnelbetween −5 to 0° C. over 2 hours. Upon completion of the addition, thepot mixture was kept at 0° C. for about 2 hours. The pot mixture wasstripped at a pot temperature of below 80° C. at 0.5 mmHg.Redistillation of product crude under reduced pressure provided thetitle compound which contained ˜50% of diglyme: b.p.: 55/1.2 mmHg,density@20° C.: 0.827, FTIR: vS-H:2140 (vs).

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

We claim:
 1. A silicon nitride or silicon carbonitride film producedfrom a hydridosilapyrrole or hydridosilaazapyrrole having formula (I):

wherein R is a substituted or unsubstituted organic group having acarbon or silicon bonded to the ring nitrogen and R′ is an alkyl group.